The pulmonary response to fibrous dusts of diverse compositions

Our plain-English summary of The pulmonary response to fibrous dusts of diverse compositions, by P. Gross, R.T. deTreville, L.J. Cralley, et al (American Industrial Hygiene Association Journal, 1970).

The study

• Authors: P. Gross, R.T. deTreville, L.J. Cralley, W.T. Granquist, F.L. Pundsack
• Journal: American Industrial Hygiene Association Journal
• Published: 1970;31(2):125-32
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001392).

In plain English

This animal experiment injected dusts directly into rats' windpipes (intratracheal injection). In total, 424 rats received one of eight fibrous dusts (fibrous quartz, natural chrysotile asbestos, tremolite talc, synthetic chrysotile, ceramic aluminum silicate, fibrous glass, brucite, silicon carbide whiskers) or a nonfibrous control, amorphous magnesium silicate. Four rats per group were killed four days after the first injection. The rest lived out their lives, though a table lists 18 silicon carbide rats as killed at intervals. With chrysotile asbestos, talc and fibrous quartz, small-airway inflammatory growths became dense collagen scars that permanently deformed bronchi and bronchioles. With the other five fibrous dusts, the main response was dust-filled scavenger cells (macrophages). Small growths appeared by day four, were fewer by day 14, were absent at six months or later, and never turned into collagen. The authors concluded that these five dusts should be classed as biologically "inert." They considered the short-lived growths an artifact of injection. They noted that such growths were not seen in earlier chrysotile inhalation studies or in their own ongoing fibrous glass inhalation study in rats and hamsters.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Animal experiment (intratracheal injection of dusts into rats, with lung tissue examined under the microscope)
• Who was studied: 424 rats in total, including the nonfibrous control group, in groups by dust type, at the Industrial Hygiene Research Unit, University of Pittsburgh. Four rats from each group were killed four days after the first injection and the rest lived out their lives. The exception is that Table 1 lists 18 silicon carbide rats as killed at intervals. Study dates are not given.
• Exposure: Intratracheal injection of fibrous quartz (microquartz), natural chrysotile asbestos (ball-milled or hammer-milled), tremolite talc (high and low nickel content), synthetic chrysotile (two batches), ceramic aluminum silicate fibers (Fiberfrax), fibrous glass (etched, uncoated, starch-coated or resin-coated), brucite, and silicon carbide whiskers, with amorphous magnesium silicate as a nonfibrous control. Most suspensions contained 3.5 mg of dust per milliliter and several contained 25 mg per milliliter. Some groups received their dose in up to four injections.
• Main results:
  • Four days after injection, lungs given asbestos, talc and microquartz showed proliferative inflammation in widely scattered smaller bronchi and bronchioles, with polypoid growths that enmeshed the injected dust.
  • In asbestos-injected lungs, similar growths also formed in the more peripheral respiratory bronchioles and alveolar ducts. These became dense collagen and shrank considerably.
  • Talc-injected lungs showed many foci of proliferative inflammation in respiratory bronchioles and alveolar ducts, similar to those in asbestos-injected lungs.
  • With synthetic chrysotile, ceramic aluminum silicate, fibrous glass, brucite and silicon carbide whiskers, the main response was a macrophage reaction. Polypoid inflammatory growths were well developed by day four, less numerous by day 14, and not found six months or more after injection.
  • The growths seen with these five dusts never turned into collagen at any time point examined.
  • Rats given the nonfibrous control (amorphous magnesium silicate) also showed occasional polypoid inflammation in respiratory bronchioles and alveolar ducts. These lesions were gone some months later, and the main response was a macrophage reaction.
  • The authors described the difference between the two groups of dusts as permanent scarring that deformed the airways (quartz, asbestos, talc) versus short-lived reversible lesions (the other fibrous dusts).
• The authors' conclusion: The authors concluded that synthetic chrysotile, fibrous glass, brucite, silicon carbide whiskers and ceramic aluminum silicate should be classed as biologically "inert." They considered the polypoid inflammation these dusts produced to be an artifact of the injection technique, which they attributed to mechanical trauma from fibers injected under pressure. They noted that such lesions were not seen in chrysotile inhalation studies cited from earlier work. Nor were they seen in the authors' own ongoing study of rats and hamsters inhaling coated and uncoated fibrous glass for over one year, cited as to be published.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Talc and vermiculite.

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• Dusts causing pneumoconiosis generate .OH and produce hemolysis by acting as Fenton catalysts — T.P. Kennedy, R. Dodson, et al. (1989)
• Relationship between chest X-ray findings and pulmonary function tests in dust workers — Y. Tonori, M. Niitsuya, et al. (2005)
• Tumorigenic effect of fibrous dusts in experimental animals — F. Pott, F. Huth, et al. (1974)
• Lung response to particulates with emphasis on asbestos and other fibrous dusts — K.P. Lee (1985)

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